.\" $Id: pvm_catchout.3,v 1.2 2001/09/27 18:51:32 pvmsrc Exp $
.TH CATCHOUT 3PVM "13 July, 1994" "" "PVM Version 3.4"
.SH NAME
pvm_catchout \- Catch output from child tasks.

.SH SYNOPSIS
.ft B
.nf
C	#include <stdio.h>

	int info = pvm_catchout( FILE *ff )
.br

Fortran	call pvmfcatchout( onoff, info )
.fi

.SH PARAMETERS
.IP ff 0.8i
File descriptor on which to write collected output.
.br
.IP onoff 0.8i
Integer parameter.  Turns output collection on or off.
.br
.IP info
Integer status code returned by the routine.
Values less than zero indicate an error.

.SH DESCRIPTION
The routine \fIpvm_catchout\fR
causes the calling task (the parent)
to catch output from any tasks spawned after the call to
\fIpvm_catchout\fR.
Characters printed on \fIstdout\fR or \fIstderr\fR in children tasks
are collected by the pvmds
and sent in control messages to the parent task,
which tags each line and appends it to the specified file.
Output from grandchildren (spawned by children) tasks
is also collected,
provided the children don't reset their \fIPvmOutputTid\fR.
.PP
If option \fIPvmShowTids\fR (see \fIpvm_setopt\fR) is true (nonzero),
output is printed as shown below,
tagged with the task id where the output originated:
.nf
	[txxxxx] BEGIN
	[txxxxx] (text from child task)
	[txxxxx] END
.fi

The output from each task includes one BEGIN line and one END line,
with whatever the task prints in between.
If PvmShowTids is false,
raw output is printed with no additional information.
.PP
In C,
the output file descriptor may be specified.
Giving a null pointer turns output collection off
for any subsequently spawned child tasks.
(Any existing output collection will still proceed at the
child tasks, until they exit or change their\fIPvmOutputTid\fR
or related settings - see man page for pvm_setopt().)
In Fortran,
output collection can only be turned on or off (again only
for subsequently spawned child tasks),
and is always logged to the stdout of the parent task.
.PP
If \fIpvm_exit\fR is called while output collection is in effect,
it will block in order to print all the output,
until all tasks sending the given task output have exited.
To avoid this,
output collection can be turned off by calling pvm_catchout(0)
before calling pvm_exit.
.PP
pvm_catchout() always returns 0.

.SH EXAMPLES
.nf
C:
	#include <stdio.h>

	pvm_catchout(stdout);
.sp
Fortran:
	CALL PVMFCATCHOUT( 1, INFO )
.fi

.SH SEE ALSO
pvm_exit(3PVM),
pvm_setopt(3PVM),
pvm_spawn(3PVM)